The present research plan aims efforts to understand between situational and personality variables affecting the person's need for cognitive closure and majors aspect of group interaction. We already know that several situational variables (time pressure, noise, fatigue, boredom) induce a need for closure, and that this need is reduced by a sense of accountability or the desirability of accurate judgments. We also know that the need for closure represent an enduring dimension of individual differences. We also know that the need for closure affect the way the individual processes information and forms opinions on a variety of topics. The present research sets out to investigate the effects need for closure may have on group interaction. A general thesis to be investigated is whether need for closure may not promote the evolution of a conservative attitude among the group members. More specifically, the following issues of interest will be investigated: I. Whether group members' need for closure induces the preference for authoritarian leadership and non-participative decision-making rules. II. Whether group members' need for closure leads to status-allocation on basis of diffuse social characteristics (e.g. gender). III. Whether group members' need for closure induces a resistance to change (represented e.g. by membership-shifts and variation in group- tasks). IV. Whether group members' need for closure affects intra-group relations, in particular those between a minority and the majority. V. Whether group members' need for closure leads to more positive attitude toward ingroup members and a greater differentiation between them and outgroup members. All the above issues bear on major ways in which individuals function in groups. Understanding those matters may have important health consequences both in terms of improving individuals' adjustment to groups, their ability to optimally function in groups and the ability of groups to optimally contribute to individuals' welfare. Altogether fifteen studies are proposed designed to allow convergent validation of the central theoretical notions through multiple operationalizations of the need for closure.